DIN EN ISO 10523:2012-04

The measurement of the pH value of water is of great importance for many types of sample. High and low pH values are toxic for aquatic organisms, either directly or indirectly. The pH value is the most useful parameter in assessing the corrosive properties of an aquatic environment. Also, it is important for the effective operation of water treatment processes and their control (for example, flocculation and chlorine disinfection), control of plumbosolvency of drinking waters and biological treatment of sewage and sewage discharges. The electrometric methods addressed in this International Standard are based on measuring the potential difference of an electrochemical cell where one of the two half-cells is a measuring electrode and the other is a reference electrode. The potential of the measuring electrode is a function of the hydrogen ion activity of the measuring solution. In view of its great practical importance, universality and exactitude, only measuring using the pH glass electrode is described in this International Standard. In the reference electrode, electrolytes applied can be in liquid, polymer or gel form. This International Standard specifies a method for determining the pH value in rain, drinking and mineral waters, bathing waters, surface and ground waters, as well as municipal and industrial waste waters, and liquid sludge, within the range pH 2 to pH 12 with an ionic strength below I = 0,3 mol/kg (conductivity: γ _{25 °C} > 2 000 mS/m) solvent and in the temperature range 0 °C to 50 °C. This standard differs from DIN 38404-5:2009-07 as follows: a) number and title of the standard have been changed; b) Annex E of DIN 38404-5:2009-07 has been included as an informative national annex; c) the standard has been editorially revised. This document has been prepared by Technical Committee ISO/TC 147 "Water quality" of the International Organization of Standardization (ISO) and has been taken over by Technical Committee CEN/TC 230 "Water Analysis", the secretariat of which is held by DIN. The responsible German committee is NA 119-01-03-01-17 AK "pH-Wert" ("pH value") of NA 119-01-03 AA "Wasseruntersuchung" ("Water Analysis") at the Water Practice Standards Committee (NAW).